Karla Mayolo-Deloisa, Jose Gonzalez-Valdez, and Marco Rito-Palomares
Biotechnol. Prog., 2016, Vol. 00, No. 00
Protein hydrophobicity can be modified after a PEGylation process. However, hydrophobic interaction chromatography (HIC) has been used to separate PEGylation reaction products less frequently than other techniques. In this context, chromatographic monoliths represent a good alternative to continue exploring the separation of PEGylated proteins with HIC. In this work, the separation of PEGylated proteins using C4 A monolith as well as Toyopearl Butyl 650C and Butyl Sepharose was analyzed. Three proteins were used as models: RNase A, b-lactoglobulin, and lysozyme. All proteins were PEGylated in the Nterminal amino groups with 20 kDa methoxy poly(ethylene glycol) propionaldehyde. The concentration of ammonium sulfate (1 M) used was the same for all stationary phases. The results obtained demonstrated that the C4 A monolith could better resolve all protein PEGylation reaction mixtures, since the peaks of mono- and di-PEGylated proteins can be clearly distinguished in the chromatographic profiles. On the contrary, while using Butyl Sepharose media only the PEGylation reaction mixtures of RNase A could be partially separated at 35 and 45 CVs. PEGylated proteins of b-lactoglobulin and lysozyme could not be resolved when Toyopearl Butyl 650C and Butyl Sepharose were used. It is then clear that monoliths are an excellent choice to explore the purification process of PEGylated proteins exploiting the advantages of HIC.
Tarasova, I. A., Lobas, A. A., Černigoj, U., Solovyeva, E. M., Mahlberg, B., Ivanov, M. V., Panić-Janković, T., Nagy, Z., Pridatchenko, M. L., Pungor, A., Nemec, B., Vidič, U., Gašperšič, J., Krajnc, N. L., Vidič, J., Gorshkov, M. V. and Mitulović, G. ELECTROPHORESIS. Accepted Author Manuscript. doi:10.1002/elps.201500489.
Affinity depletion of abundant proteins such as human serum albumin (HSA) is an important stage in routine sample preparation prior to tandem mass spectrometry (MS/MS) analysis of biological samples with high range of concentrations. Due to the charge competition effects in electrospray ion source that results in discrimination of the low-abundance species, as well as limited dynamic range of MS/MS, restricted typically by three orders of magnitude, the identification of low-abundance proteins becomes a challenge unless the sample is depleted from high concentration compounds. This dictates a need for developing efficient separation technologies allowing fast and automated protein depletion. In this study we performed evaluation of a novel immunoaffinity-based CIMac depletion column with specificity to HSA (CIMac-αHSA). Because of the convective flow-through channels, the polymethacrylate CIMac monoliths afford flow rate-independent binding capacity and resolution that results in relatively short analysis time compared with traditional chromatographic supports. Seppro IgY14 depletion kit was used as a benchmark to control the results of depletion. Bottom-up proteomic approach followed by label-free quantitation using normalized spectral indexes were employed for protein quantification in G1/G2 and Cleavage/Blastocyst IVF culture media widely utilized in clinics for embryo growth in vitro. The results revealed approximately equal HSA level of 100% ± 25% in albumin-enriched fractions relative to the non-depleted samples for both CIMac-αHSA column and Seppro kit. In the albumin-free fractions concentrated 5.5-fold by volume, serum albumin was identified at the levels of 5 to 30% and 20 to 30% for the CIMac-αHSA and Seppro IgY14 spin columns, respectively.
P. Stepperta, D. Burgstallera, M. Klausbergera, E. Bergerb, P.P. Aguilara, T.A. Schneiderb, P. Krambergerc, A. Toverd, K. Nöbauere, E. Razzazi-Fazelie, A. Jungbauer, Journal of Chromatography A, 1455 (2016)
Enveloped virus-like particles (VLPs) are increasingly used as vaccines and immunotherapeutics. Frequently, very time consuming density gradient centrifugation techniques are used for purification ofVLPs. However, the progress towards optimized large-scale VLP production increased the demand for fast, cost efficient and scaleable purification processes. We developed a chromatographic procedure for purification of HIV-1 gag VLPs produced in CHOcells. The clarified and filtered cell culture supernatant was directly processed on an anion-exchange monolith. The majority of host cell impurities passed throughthe column, whereas the VLPs were eluted by a linear or step salt gradient; the major fraction of DNA waseluted prior to VLPs and particles in the range of 100–200nm in diameter could be separated into two fractions. The earlier eluted fraction was enriched with extracellular particles associated to exosomes or microvesicles, whereas the late eluting fractions contained the majority of most pure HIV-1 gag VLPs. DNA content in the exosome-containing fraction could not be reduced by Benzonase treatment which indicated that the DNA was encapsulated. Many exosome markers were identified by proteomic analysisin this fraction. We present a laboratory method that could serve as a basis for rapid downstream processing of enveloped VLPs. Up to 2000 doses, each containing 1×109 particles, could be processed witha 1mL monolith within 47 min. The method compared to density gradient centrifugation has a 220-fold improvement in productivity.
U. Cernigoj, U. Vidic, B. Nemec, J. Gaspersic, J. Vidic,N. L. Krajnc, A. Strancar, A. Podgornik. Journal of Chromatography A, 1464 (2016) 72–78
We investigated effect of immobilization procedure and monolith structure on chromatographic performance of methacrylate monoliths bearing affinity ligands. Monoliths of different pore size and variousaffinity ligands were prepared and characterized using physical and chromatographic methods. When testing protein A monoliths with different protein A ligand densities, a significant non linear effect ofligand density on dynamic binding capacity (DBC) for IgG was obtained and accurately described by Langmuir isotherm curve enabling estimation of protein A utilization as a function of ligand density. Maximal IgG binding capacity was found to be at least 12 mg/mL exceeding theoretical monolayer adsorption value of 7.8 mg/mL assuming hexagonal packing and IgG hydrodynamic diameter of 11 nm. Observed discrepancy was explained by shrinkage of IgG during adsorption on protein A experimentally determined through calculated adsorbed IgG layer thickness of 5.4 nm from pressure drop data. For monoliths with different pore size maximal immobilized densities of protein A as well as IgG dynamic capacitylinearly correlates with monolith surface area indicating constant ligand utilization. Finally, IgGs toward different plasma proteins were immobilized via the hydrazide coupling chemistry to provide oriented immobilization. DBC was found to be flow independent and was increasing with the size of bound protein. Despite DBC was lower than IgG capacity to immobilized protein A, ligand utilization was higher.
I. T. Akmacic,B. Nemec,U. Vidic, S. Malcic, K. Miklic, U. Cernigoj, J. Vidic, N. L. Krajnc, A. Strancar, G. Lauc, T. L. Rovis, M. P. Bakovic. Croat. Chem. Acta 2016, 89(2)
Changes in protein glycosylation are related to different diseases and have a potential as diagnostic and prognostic disease biomarkers. Transferrin (Tf) glycosylation changes are common marker for congenital disorders of glycosylation. However, biological interindividual variability of Tf N-glycosylation and genes involved in glycosylation regulation are not known. Therefore, high-throughput Tf isolation method and large scale glycosylation studies are needed in order to address these questions. Due to their unique chromatographic properties, the use of chromatographic monoliths enables very fast analysis cycle, thus significantly increasing sample preparation throughput. Here, we are describing characterization of novel immunoaffinity-based monolithic columns in a 96-well plate format for specific highthroughput purification of human Tf from blood plasma. We optimized the isolation and glycan preparation procedure for subsequent ultra performance liquid chromatography (UPLC) analysis of Tf N-glycosylation and managed to increase the sensitivity for approximately three times compared to initial experimental conditions, with very good reproducibility.
J. Transfiguracion, A. P. Manceur, E. Petiot, C. M. Thompson, A. A. Kamen
The influenza virus continuously undergoes antigenic evolution requiring manufacturing, validation and release of new seasonal vaccine lots to match new circulating strains. Although current production processes are well established for manufacturing seasonal inactivated influenza vaccines, significant limitations have been underlined in the case of pandemic outbreaks. The World Health Organization called for a global pandemic influenza vaccine action plan including the development of new technologies. A rapid and reliable method for the quantification of influenza total particles is crucially needed to support the development, improvement and validation of novel influenza vaccine manufacturing platforms. This work presents the development of an ion exchange-high performance liquid chromatography method for the quantification of influenza virus particles. The method was developed using sucrose cushion purified influenza viruses A and B produced in HEK 293 suspension cell cultures. The virus was eluted in 1.5 M NaCl salt with 20 mM Tris–HCl and 0.01% Zwittergent at pH 8.0. It was detected by native fluorescence and the total analysis time was 13.5 min. A linear response range was established between 1 × 109 and 1 × 1011 virus particle per ml (VP/ml) with a correlation coefficient greater than 0.99. The limit of detection was between 2.07 × 108 and 4.35 × 109 whereas the limit of quantification was between 6.90 × 108 and 1.45 × 1010 VP/ml, respectively. The coefficient of variation of the intra- and inter-day precision of the method was less than 5% and 10%. HPLC data compared well with results obtained by electron microscopy, HA assay and with a virus counter, and was used to monitor virus concentrations in the supernatant obtained directly from the cell culture production vessels. The HPLC influenza virus analytical method can potentially be suitable as an in-process monitoring tool to accelerate the development of processes for the manufacturing of influenza vaccines.
A.M. Almeida, J.A. Queiroz, F. Sousa, A. Sousa
Journal of Chromatography B, 978–979 (2015) 145–150
The progress of DNA vaccines is dependent on the development of suitable chromatographic procedures to successfully purify genetic vectors, such as plasmid DNA. Human Papillomavirus is associated with the development of tumours due to the oncogenic power of E6 and E7 proteins, produced by this virus. The supercoiled HPV-16 E6/E7 plasmid-based vaccine was recently purified with the arginine monolith, with 100% of purity, but only 39% of recovery was achieved. Therefore, the present study describes the application of experimental design tools, a newly explored methodology in preparative chromatography, in order to improve the supercoiled plasmid DNA recovery with the arginine monolith, maintaining the high purity degree. In addition, the importance and influence of pH in the pDNA retention to the arginine ligand was also demonstrated. The Composite Central Face design was validated and the recovery of the target molecule was successfully improved from 39% to 83.5%, with an outstanding increase of more than double, while maintaining 100% of purity.
J-P Pirnay et al.
Pharm Res, Springer, 14 Jan 2015
The worldwide antibiotic crisis has led to a renewed interest in phage therapy. Since time immemorial phages control bacterial populations on Earth. Potent lytic phages against bacterial pathogens can be isolated from the environment or selected from a collection in a matter of days. In addition, phages have the capacity to rapidly overcome bacterial resistances, which will inevitably emerge.
To maximally exploit these advantage phages have over conventional drugs such as antibiotics, it is important that sustainable phage products are not submitted to the conventional long medicinal product development and licensing pathway. There is a need for an adapted framework, including realistic production and quality and safety requirements, that allows a timely supplying of phage therapy products for 'personalized therapy' or for public health or medical emergencies.
This paper enumerates all phage therapy product related quality and safety risks known to the authors, as well as the tests that can be performed to minimize these risks, only to the extent needed to protect the patients and to allow and advance responsible phage therapy and research.
D. Buzzi, A. Štrancar
Chimica Oggi-Chemistry Today; Vol 33(1) January/February 2015
The importance of the monitoring of a process all along its steps by means of PAT has been defined by FDA in 2002. How can be defined the product quality and what are the parameters that should be checked by means of different analysis techniques, being focused in particular on the application of high pressure liquid chromatography techniques (HPLC) as high value tool for the process monitoring. From the first introduction of Process Analytical Technology to the "state of the art": how can be PAT implemented in order to ensure the final product quality.
J. Ruscic, I. Gutiérrez-Aguirre, M. Tusek Znidaric, S. Kolundzija, A. Slana, M. Barut, M. Ravnikar, M. Krajacic
Journal of Chromatography A, 1388 (2015) 69–78
The emergence of next-generation "deep" sequencing has enabled the study of virus populations with much higher resolutions. This new tool increases the possibility of observing mixed infections caused by combinations of plant viruses, which are likely to occur more frequently than previously thought. The bio-logical impact of co-infecting viruses on their host has yet to be determined and fully understood, and the first step towards reaching this goal is the separation and purification of individual species. Ion-exchange monolith chromatography has been used successfully for the purification and concentration of different viruses, and number of them have been separated from plant homogenate or bacterial and eukaryoticlysate. Thus, the question remained as to whether different virus species present in a single sample could be separated. In this study, anion-exchange chromatography using monolithic supports was optimized for fast and efficient partial purification of three model plant viruses: Turnip yellow mosaic virus, Tomato bushy stunt virus, and Tobacco mosaic virus. The virus species, as well as two virus strains, were separated from each other in a single chromatographic experiment from an artificially mixed sample. Based on A260/280 ratios, we were able to attribute specific peaks to a certain viral morphology/structure (icosa-hedral or rod-shaped). This first separation of individual viruses from an artificially prepared laboratory mixture should encourage new applications of monolithic chromatographic supports in the separation of plant, bacterial, or animal viruses from all kinds of mixed samples.
Zunyang Ke, Yu Wang and Zhongming Li
Anion-exchange chromatography is a key capture step in downstream processing plasmid DNA (pDNA). Separation of pDNA using traditional particle-based anion-exchange supports is usually slow and has a low capacity for pDNA due to steric exclusion effects. Due to convective mass transfer properties, and large flow-through channels for binding large biomolecules, monoliths have been shown to provide a fast and efficient alternative for pDNA purification. This study describes the use of monoliths for purification of a therapeutic pDNA vaccine against multidrug resistant tuberculosis (MDR TB).
P. Kramberger, U. Lidija, A. Štrancar
Human Vaccines & Immunotherapeutics, 11:4 (2015) 1010-1021
Downstream processing of nanoplexes (viruses, virus-like particles, bacteriophages) is characterized by complexity of the starting material, number of purification methods to choose from, regulations that are setting the frame for the final product and analytical methods for upstream and downstream monitoring. This review gives an overview on the nanoplex downstream challenges and chromatography based analytical methods for efficient monitoring of the nanoplex production.
M. Zaveckas, S. Snipaitis, H. Pesliakas, J. Nainys, A. Gedvilaite
Journal of Chromatography B, 991 (2015) 21–28
Diseases associated with porcine circovirus type 2 (PCV2) infection are having a severe economic impacton swine-producing countries. The PCV2 capsid (Cap) protein expressed in eukaryotic systems self-assemble into virus-like particles (VLPs) which can serve as antigens for diagnostics or/and as vaccinecandidates. In this work, conventional adsorbents as well as a monolithic support with large pore sizeswere examined for the chromatographic purification of PCV2 Cap VLPs from clarified yeast lysate. QSepharose XL was used for the initial separation of VLPs from residual host nucleic acids and some hostcell proteins. For the further purification of PCV2 Cap VLPs, SP Sepharose XL, Heparin Sepharose CL-6Band CIMmultus SO3 monolith were tested. VLPs were not retained on SP Sepharose XL. The purity of VLPsafter chromatography on Heparin Sepharose CL-6B was only 4–7% and the recovery of VLPs was 5–7%.Using ion-exchange chromatography on the CIMmultus SO3 monolith, PCV2 Cap VLPs with the purityof about 40% were obtained. The recovery of VLPs after chromatography on the CIMmultus SO3 mono-lith was 15–18%. The self-assembly of purified PCV2 Cap protein into VLPs was confirmed by electronmicroscopy. Two-step chromatographic purification procedure of PCV2 Cap VLPs from yeast lysate wasdeveloped using Q Sepharose XL and cation-exchange CIMmultus SO3 monolith.
L. Hernandez, D. Stewart, L. Zumalacarregui, D. Amaro
Chinese Journal of Chromatography A, 1000-8713 (2015) 642-646
Affinity and ion exchange conventional chromatography have been used to capture erythropoietin (EPO) from mammalian cell culture supernatant. Currently, chromatographic adsorbent perfusion is available, however a limited number of applications have been found in the literature. In this work, three anion exchange chromatographic supports (gel, membrane and monolithic) were evaluated in the capture step of the recombinant erythropoietin purification process. The influences of load and flow rate on each support performance were analyzed. Also the purity of the EPO molecules was determined. A productivity analysis, as a decision tool for larger scale implementation, was done. As a conclusion, the evaluated supports are technically suitable to capture EPO with adequate recovery and good purity. However, the monolithic column admits high operating velocity, showing the highest adsorption capacity and productivity.
A. G. Lopes
FBP-461, Food and Bioproducts Processing (2014)
As the biopharmaceutical industry matures, the trend towards increased flexibility and productivity, faster time tomarket and greater profitability are driving the replacement of traditional stainless steel equipment by single-use technology (SUT). The use of SUT in the biopharmaceutical industry can significantly impact the manufacturing process efficiency by reducing capital costs, improving plant flexibility, reducing start-up times and costs, and elim-inating both non-value added process steps and the risk of cross-contamination. In addition it significantly reduces process liquid waste, labour costs and on-site quality and validation requirements. This paper reviews the current status of the technology and the impact of SUT in the biopharmaceutical industry, with the aim of identifying the challenges and limitations that still need to be addressed for further adoption of these technologies. Even tough SUT has a multitude of systems available, its components and assemblies have little standardisation as well as alack of harmonised tests and procedures among suppliers, with an array of guidelines from a variety of sourcesand no critical limits have been established. In addition, the use of SUT has new validation requirements such as leachables and extractables, suppliers’ qualification and SUT lot-to-lot variability. The lack of expertise in these areas and the new training requirements when using SUT also need to be addressed. To date the majority of the avail-able literature regarding SUT is found in trade journals where typically suppliers are the main contributors. There is still a lack of engagement of the academic community, which contributes to very limited scientific proof from independent peer-reviewed research to support performance of SUT. This is particularly the case during operation and integrity testing of SUT, during for example on-site testing, transport and disposal. Another area where no work has been undertaken concerns conceptual approaches for facility clean-room requirement and appropriate layout design using SUT. Investment in novel technologies, research, standardisation and training is paramount for further development and implementation of SUTs across all sectors of the biopharmaceutical industry.
Urh Černigoj, Urška Martinuč, Sara Cardoso, Rok Sekirnik, Nika Lendero Krajnc, Aleš Štrancar
Sample displacement chromatography (SDC) is a chromatographic technique that utilises different rela-tive binding affinities of components in a sample mixture and has been widely studied in the context ofpeptide and protein purification. Here, we report a use of SDC to separate plasmid DNA (pDNA) isoformsunder overloading conditions, where supercoiled (sc) isoform acts as a displacer of open circular (oc) orlinear isoform. Since displacement is more efficient when mass transfer between stationary and mobilechromatographic phases is not limited by diffusion, we investigated convective interaction media (CIM)monoliths as stationary phases for pDNA isoform separation. CIM monoliths with different hydrophobic-ities and thus different binding affinities for pDNA (CIM C4 HLD, CIM-histamine and CIM-pyridine) weretested under hydrophobic interaction chromatography (HIC) conditions. SD efficiency for pDNA isoformseparation was shown to be dependent on column selectivity for individual isoform, column efficiencyand on ammonium sulfate (AS) concentration in loading buffer (binding strength). SD and negative modeelution often operate in parallel, therefore negative mode elution additionally influences the efficiencyof the overall purification process. Optimisation of chromatographic conditions achieved 98% sc pDNAhomogeneity and a dynamic binding capacity of over 1 mg/mL at a relatively low concentration of AS.SDC was successfully implemented for the enrichment of sc pDNA for plasmid vectors of different sizes,and for separation of linear and and sc isoforms, independently of oc:sc isoform ratio, and flow-rate used.This study therefore identifies SDC as a promising new approach to large-scale pDNA purification, whichis compatible with continuous, multicolumn chromatography systems, and could therefore be used toincrease productivity of pDNA production in the future.
P. Leblebici, M. E. Leblebici, F. Ferreira-da-Silva, A. E.Rodrigues, L. S. Pais
Journal of Chromatography B, 962 (2014) 89-93
Monolithic columns have attracted significant attention for the purification of large biomolecules. In the present study, a step gradient elution method was evaluated for the separation of human immunoglobulinG (hIgG) into its subclasses on CIM (convective interaction media) r-protein A (recombinant protein A)monolithic column. hIgG was loaded onto the column and bound protein was eluted with a pH gra-dient. The subclass content of the eluted fractions was analyzed by enzyme-linked immunosorbentassay (ELISA). Results showed that separation of IgG3 from the other three subclasses can be success-fully achieved with high selectivity (100%) and throughput on monolithic media. It was also revealedthat enriched fractions of IgG1 and IgG2 could be obtained from purified hIgG in a 28 min long chro-matographic run. Three fractions with high IgG1 content (89.1%, 94.3% and 88.8%) were recovered. Furthermore, IgG2 was enriched to 64% successfully. A rapid step gradient elution scheme without any additives in buffers was proven to obtain enriched preparations of the two important subclasses with high throughput. The separation time can be reduced even more by increasing the flow rate without anyloss in selectivity, which will be beneficial in industrial scale applications.
M. M. St. Amand, B. A. Ogunnaike, A.S. Robinson
Published online in Wiley Online Library, 2013
One major challenge currently facing the biopharmaceutical industry is to understand how MAb microheterogeneity affects therapeutic efficacy, potency, immunogenicity, and clearance. MAb micro-heterogeneity can result from post-translational modifications such as sialylation, galactosylation, C-terminal lysine cleavage, glycine amidation, and tryptophan oxidation, each of which can generate MAb charge variants; such heterogeneity can affect pharmacokinetics (PK) considerably. Implementation of appropriate on-line quality control strategies may help to regulate bioprocesses, thus enabling more homogenous material with desired posttranslational modifications and PK behavior. However, one major restriction to implementation of quality control strategies is the availability of techniques for obtaining on-line or at line measurements of these attributes. In this work, we describe the development of an at-line assay to separate MAb charge variants in near real-time, which could ultimately be used to implement on-line quality control strategies for MAb production. The assay consists of a 2DHPLC method with sequential in-line Protein A and WCX-10 HPLC column steps. To perform the 2D-HPLC assay at-line, the two columns steps were integrated into a single method using
a novel system configuration that allowed parallel flow over column 1 or column 2 or sequential flow from column 1 to column 2. A bioreactor system was also developed such that media samples could be removed automatically from bioreactor vessels during production and delivered
to the 2D-HPLC for analysis. With this at-line HPLC assay, we have demonstrated that MAb microheterogeneity occurs throughout the cell cycle whether the host cell line is grown under different or the same nominal culture conditions.
M. M. Segura, M. Puig, J. Piedra, S. Miravet
Adenovirus: Methods and protocols, Methods in Molecular Biology, vol. 1089
Adenovirus vectors are efficient gene delivery tools. A major caveat with vectors derived from common human adenovirus serotypes is that most adults are likely to have been exposed to the wild-type virus and exhibit active immunity against the vectors. This preexisting immunity limits their clinical success. Strategies to circumvent this problem include the use of nonhuman adenovirus vectors. Vectors derived from canine adenovirus type 2 (CAV-2) are among the best-studied representatives. CAV-2 vectors are particularly attractive for the treatment of neurodegenerative disorders. In addition, CAV-2 vectors have shown great promise as oncolytic agents in virotherapy approaches and as vectors for recombinant vaccines. The rising interest in CAV-2 vectors calls for the development of scalable GMP compliant production and purification strategies. A detailed protocol describing a complete scalable downstream processing strategy for CAV-2 vectors is reported here. Clarification of CAV-2 particles is achieved by microfiltration. CAV-2 particles are subsequently concentrated and partially purified by ultrafiltration–diafiltration. A Benzonase® digestion step is carried out between ultrafiltration and diafiltration operations to eliminate contaminating nucleic acids. Chromatography purification is accomplished in two consecutive steps. CAV-2 particles are first captured and concentrated on a propyl hydrophobic interaction chromatography column followed by a polishing step using DEAE anion exchange monoliths. Using this protocol, high-quality CAV-2 vector preparations containing low levels of contamination with empty viral capsids and other inactive vector forms are typically obtained. The complete process yield was estimated to be 38–45 %.
F. W. Krainer, R. Pletzenauer, L. Rossetti, C. Herwig, A. Glieder, O. Spadiut
Protein Expression and Purification 95 (2014) 104–112
The plant enzyme horseradish peroxidase (HRP) is used in several important industrial and medical applications, of which especially biosensors and diagnostic kits describe an emerging field. Although there is an increasing demand for high amounts of pure enzyme preparations, HRP is still isolated from the plant as a mixture of different isoenzymes with different biochemical properties. Based on a recent next generation sequencing approach of the horseradish transcriptome, we produced 19 individual HRP isoenzymes recombinantly in the yeast Pichia pastoris. After optimizing a previously reported 2-step purification strategy for the recombinant isoenzyme HRP C1A by substituting an unfavorable size exclusion chromatography step with an anion exchange step using a monolithic column, we purified the 19 HRP isoenzymes with varying success. Subsequent basic biochemical characterization revealed differences in catalytic activity, substrate specificity and thermal stability of the purified HRP preparations. The preparations of the isoenzymes HRP A2A and HRP A2B were found to be highly interesting candidates for future applications in diagnostic kits with increased sensitivity.